1. Field of the Invention
The present invention relates to an air-actuated valve of a gas container, and especially to an apparatus for detecting whether an air tube for applying a pneumatic pressure is connected to an air-actuated valve.
2. Description of Related Art
Spiral material gas for use in manufacture of semiconductors is usually stored in a portable gas container which is called "a gas bomb" or "a gas cylinder". Many special material gases for use in manufacture of semiconductors are dangerous gases which possess combustibility (explosiveness), toxicity, corrosiveness or combustion-supporting property. It is therefore necessary to take thoughtful consideration to their use in view of safety. Accordingly, a gas container filled with such a dangerous special material gas has hitherto been accommodated in a box having an exhaust duct to cope with a gas leakage in an emergency. This box is called "a cylinder cabinet".
When a gas container is accommodated in a cylinder cabinet, it is desired that the opening and closing operation of a valve on the gas container is automatically carried out by remote operation in view of safety. There have been hitherto used various valves capable of being handled under remote operation. A conventional valve of the remote operation type is an air-actuated valve. An air-actuated valve is opened or closed by moving a valve body by a pneumatic actuator. An air-actuated valve for a gas container is normally a closed type. It is constructed such that the valve is opened only when compressed air is supplied to the pneumatic actuator.
When a gas container is removed for exchange from a process line, the remaining gas in the line is purged to prevent the special material gas from leaking out of the line. This purging work must be carried when the valve of the gas container is closed. In the case of an air-actuated valve, the closing of said valve has hitherto been effected by stopping the supply of compressed air thereto. When an air tube is connected to an air-actuated valve, however, it is feared that compressed air will be supplied to the valve because of a manual operation mistake, or an air control circuit malfunction. Accordingly, the purging work is premised on the assumption that the air tube was previously detached from the air-actuated valve.
Since the detachment of an air tube is manual work carried out by an operator, the operator may forget to detach the air tube in error. Although there is, of course, no problem even in this case because it is devised that the supply of compressed air is automatically stopped in purge, it is desirable, from the viewpoint of multiplexing fail safe, to cope with a serious situation.